Occurrence of primarily noninducible atrioventricular nodal reentry tachycardia after radiofrequency delivery in the slow pathway region during empirical slow pathway modulation

Abstract

Background

The first‐line therapy for atrioventricular nodal reentry tachycardia (AVNRT) is catheter‐based slow pathway modulation. If AVNRT is not inducible during an electrophysiological study, an empirical slow pathway modulation (ESPM) may be considered in patients with dual atrioventricular nodal physiology and/or a typical electrocardiogram (ECG).

Methods

We screened 149 symptomatic patients who underwent ESPM in our department between 1993 and 2013. All patients fulfilled the following criteria: (1) either dual atrioventricular nodal (AVN) physiology with up to 2 AVN echo beats or characteristic ECG documentation or both, (2) noninducibility of AVNRT by programmed stimulation, and (3) completion of a telephone questionnaire for long‐term follow‐up. Out of this population we retrospectively investigated 13 patients who were primarily noninducible but in whom an AVNRT occurred during or after radiofrequency (RF) delivery.

Results

When AVNRT occurred, the procedure lost its empirical character, and RF delivery was continued until the procedural endpoint of noninducibility of AVNRT. This endpoint was reached in all but one patient (92%). After a follow‐up of 73 ± 15 months, this patient was the only one who reported no benefit from the procedure.

Conclusions

Out of 149 initially noninducible patients, a considerable number (9%) exhibited AVNRT during or after RF delivery. These patients crossed over from empirical to controlled slow pathway modulation resulting in a good clinical outcome. Our observations should encourage electrophysiologists to repeat programmed stimulation even after initial empirical RF delivery to retest for inducibility.

1. INTRODUCTION

Atrioventricular nodal reentry (AVNRT) is the most common mechanism of paroxysmal tachycardia. An induction of AVNRT during an electrophysiological study is crucial to distinguish it from differential diagnoses such as atrioventricular tachycardia or atrial tachycardia. If induction is achieved, the therapy of choice is a catheter‐based modulation of the slow pathway of the atrioventricular (AV) node. If induction is impossible despite thorough programmed atrial stimulation with and without pharmacological provocation (eg, orciprenaline or atropine), an empirical radiofrequency (RF) impulse delivery may be considered if dual AV nodal physiology and/or a characteristic electrocardiogram (ECG) documentation are present.1, 2, 3, 4, 5 However, during RF delivery, the patient is exposed to complications such as complete AV block. Furthermore, a valid prediction of the outcome is impossible, because the diagnosis of the clinical tachycardia remains uncertain. Most importantly, the control conditions for the procedural endpoint, which under nonempirical conditions is the noninducibility of AVNRT, are lacking. Consistently, a recent survey revealed controversial opinions of clinical electrophysiologists on whether or not to ablate under empirical conditions.6

Usually, programmed atrial stimulation with up to 2 extra beats of decreasing coupling intervals is used to induce AVNRT. This can be combined with pharmacological provocation by application of orciprenaline or atropine. However, despite these measures, a considerable number of patients remain uninducible.^2–5,7

We here present procedural data and long‐term outcome of a series of 13 patients in whom AVNRT could primarily not be induced but in whom AVNRT occurred during or after empirical initial RF delivery in the slow pathway region.

2. METHODS and Results

2.1. Study design

Out of 3003 patients who underwent slow pathway modulation in our department over a period of 20 years (1993–2013), 149 patients who were not inducible by conventional means and who subsequently underwent empirical slow pathway modulation were retrospectively evaluated. All patients fulfilled the following criteria: (1) either dual atrioventricular nodal (AVN) physiology with 2 or less AVN echos or characteristic ECG documentation or both; (2) noninducibility of a supraventricular tachycardia (SVT) by programmed atrial stimulation with and without pharmacological stimulation; and (3) completion of a telephone questionnaire for long‐term follow‐up. Out of these, we retrospectively included 13 patients (Table 1) in whom AVNRT occurred during or after initial RF delivery. The diagnostic criteria applied for AVNRT diagnosis were narrow complex tachycardia with regular cycle lengths and short ventriculoatrial (VA) interval. Two patients had received a prior electrophysiological study (EPS). Out of these, one had received a slow pathway modulation due to inducible AVNRT. The 13 patients presented in this study were part of the populations of two previous studies from our group investigating characteristics and success rates of empirical slow pathway modulation.4, 5 However, these studies did not specifically analyze in detail those patients in whom AVNRT occurred during or after RF delivery.

Table 1.

Patient characteristics and comorbidities

No. of patients	13
Median age at empirical slow pathway modulation, yr	54
Median age at manifestation of symptomatic tachycardia, yr	36
Sex (female/male)	7/6 (54%/46%)
Patients with cardiovascular comorbidities	6 (46%)
Coronary heart disease	2 (15%)
Diabetes	1 (8%)
Hypertension	6 (46%)
Patients with prediagnosed arrhythmia other than AVNRT	0

Abbreviations: AVNRT, atrioventricular nodal reentry tachycardia.

2.2. EPS

Details of the procedures have been reported previously.4, 5 The EPS including RF delivery had a mean duration of 122 ± 11 min. As previously reported, programmed stimulation with one (S2) and subsequently with two (S2S3) premature beats was applied. The basic stimulation cycle length (S1) was gradually reduced during the protocol from a maximum of 600 ms to a minimum of 330 ms or until the Wenckebach point was reached. If this failed to induce an SVT, orciprenaline (0.25‐mg bolus) was added intravenously, which was usually repeated if AVNRT was still not inducible. One patient was additionally given adenosine (18 mg) to exclude an accessory pathway. There was no evidence for an accessory pathway in any of the patients. None of the 13 patients was inducible using this protocol.

2.3. Surface ECG documentation and dual nodal pathway physiology prior to empirical slow pathway modulation

Nine of the patients had a surface ECG or Holter documentation of a tachycardia compatible with an AVNRT. Eleven patients exhibited dual nodal pathway physiology either in the form of an atriohis (AH) jump, one or two echo beats, or a combination of both. Seven patients exhibited both dual nodal pathway physiology and an ECG documentation (Table 2). Based on these criteria and their symptoms, all patients were selected for empirical slow pathway modulation.

Table 2.

Distribution of diagnostic criteria in the patient population

Patient Group	No.
All patients	13
Patients with ECG/Holter documentation of AVNRT	9
Patients with DNPP in form of 1 AVN echo and/or an AH jump during EPS	4
Patients with DNPP in form of 2 AVN echos	7
Patients with both DNPP and ECG/Holter documentation	7

Abbreviations: AVN, atrioventricular nodal; AVNRT, atrioventricular nodal reentry tachycardia; DNPP, dual AV nodal pathway physiology; ECG, electrocardiogram; EPS, electrophysiological study.

2.4. Slow pathway modulation and procedural outcome

Since in none of the patients AVNRT was inducible, the initial RF delivery was attempted as an empirical treatment of the suspected but yet uncertain diagnosis of AVNRT. RF delivery (maximum energy of 50 W) was applied with the initial intent to induce a junctional rhythm as evidence for slow pathway injury. In all patients, AVNRT occurred during or after the first or subsequent RF deliveries. Since at this moment the diagnosis of AVNRT was secured, the procedure lost its empirical character. RF delivery in the slow pathway region was now continued until AVNRT did not occur anymore and was not inducible anymore by conventional means such as programmed stimulation. This consolidated a new procedural controlled endpoint that did not exist before the first RF delivery. This endpoint was reached in 12 (92%) of the patients (Figure 1). The residual occurrence of an AH jump and/or of one AV nodal echo was tolerated after RF delivery, because slow pathway modulation and not slow pathway ablation was intended. All other procedural aspects including catheter placement and mapping of the slow pathway region were conducted as previously reported.4, 5 No severe complications requiring further treatment occurred. One patient exhibited a transient second degree Wenckebach AV block, which recovered during the remainder of the EPS. In this patient, the endpoint of elimination of AVNRT was not reached. In one patient we switched to cryoablation, because during RF delivery single beats were not conducted via the AV node, aiming to minimize the risk for permanent AV block.

Figure 1.

Success rates of slow pathway modulation after occurrence of AVNRT during or after RF delivery. The left bar shows the procedural success rate (ie, the number of patients in which the procedural endpoint of noninducibility of AVNRT was reached). The right bar depicts the long‐term clinical outcome after a mean follow‐up time of 73 ± 15 months. Abbreviations: AVNRT, atrioventricular nodal reentry tachycardia

2.5. Long‐term outcome

A follow‐up in form of a telephone questionnaire was conducted after a mean time of 73 ± 15 months. Patients were questioned whether they had felt a recurrence of any kind of arrhythmia after the procedure. Those patients who answered with yes were asked for (1) the symptomatic intensity and quality, (2) the frequency of occurrence, and (3) the duration of the arrhythmic episodes. All but one patient felt a significant benefit from the procedure (92%) (Figure 1). This was the same patient in whom the procedural endpoint of slow pathway modulation (ie, noninducibility of AVNRT) had not been reached. Seven (54%) of the patients reported a complete absence of any subjectively felt significant arrhythmias since the time of the procedure. Five patients (38%) still subjectively felt arrhythmias, but either reported a reduction of the frequency of occurrence, or a reduction of the duration or the intensity, or a change in quality of the episodes. These patients also felt a benefit from the procedure and ascribed an improvement of their clinical condition to the procedure.

3. DISCUSSION

We here report on 13 symptomatic patients in whom SVT was not inducible by conventional means but in whom an AVNRT occurred during or after RF delivery in the setting of empirical slow pathway modulation.

3.1. Short‐ and long‐term success rates

In the patients presented in our study, the occurrence of AVNRT during or after RF delivery came as an unexpected finding. Once this was observed, the patient crossed over from an empirical (ie, uncontrolled) to a controlled nonempirical slow pathway modulation. Therefore, RF delivery was continued with the endpoint of noninducibility of AVNRT. This endpoint was reached in all but one patient, and this patient was also the only patient who did not benefit from the procedure in the long term. This success rate (92%) comes close to the short‐ and long‐term success rates of nonempirical slow pathway modulation (ie, inducible AVNRT).1, 8, 9, 10, 11

3.2. Should RF delivery be used as a diagnostic tool to induce AVNRT?

Yamini Sharif et al. have performed RF delivery with the primary intent of inducing AVNRT,7 a method that has been controversially discussed.12 It has to be emphasized that this was not the case in our patients, in whom RF was applied to perform an empirical slow pathway modulation with curative intent and in whom AVNRT occurred unexpectedly.

In our patient population, the decision to perform slow pathway modulation was made before the first RF delivery, when it became clear that the patients were not inducible during EPS. As additional preconditions, they also had to exhibit either dual AVN physiology or an ECG documentation consistent with AVNRT, or both of these features, and they had to exhibit relevant symptoms. These conditions are similar to the requirements of other studies that have performed empirical slow pathway modulation.2, 3, 4, 5 We did not use RF delivery in the slow pathway region as a purely diagnostic tool. Moreover, we believe that all patients in whom RF is applied in the slow pathway region should be carefully selected and should qualify for an empirical slow pathway modulation with curative intent in advance of the first RF delivery. This has to be carefully determined for each individual patient considering preinterventional diagnostic criteria such as dual nodal pathway physiology, ECG documentation, and of course the severity of symptoms.

3.3. Clinical Implications

The most significant finding of our study is that out of 149 patients who were not inducible, almost 1 out of 10 patients exhibited AVNRT during or after RF delivery. Other than in the usual nonempirical setting, where AVNRT is inducible before RF delivery, an electrophysiologist may be tempted to omit programmed stimulation in an empirical setting in the belief that, if AVNRT was not inducible before RF delivery, it will not be inducible after RF delivery either. Our data show that this is not necessarily the case and emphasize that programmed stimulation after each RF is necessary even when AVNRT was not inducible before RF delivery. This may offer the opportunity for a considerable number of patients to cross over from empirical to controlled RF delivery with intent for slow pathway modulation with a presumably better outcome.

3.4. Limitations of the study

This is a retrospective study reporting a subgroup of 13 patients with RF‐induced AVNRT out of 149 patients who underwent empirical slow pathway modulation during a period from 1993 to 2013. Thus, the usual limitations of a retrospective analysis apply. Due to the low number of patients, statistical methods were not applied. However, empirical slow pathway modulation is a rare procedure, and the constellation investigated in this study (ie, occurrence of AVNRT during or after RF delivery) is even rarer, thus making the collection of a larger number of patients difficult.

Conflicts of interest

F.K.W., N.B., P.L., G.F., D.G.D., S.K., P.S.L., J.K., K.W., G.M., L.E. and C.P. have received lecture honoraria and/or travel grants from Astra/Zeneca, Bayer, Biosense Webster, Biotronik, Boehringer Ingelheim, Boston Scientific, Medtronic, Sanofi Aventis, Sorin, and/or St. Jude Medical. L.E. has received research grants from Biotronik, St. Jude Medical, Sanofi, and Osypka. G.F. is supported by Osypka. N.B. is supported by a fellowship from Boston Scientific. C.P. has received grants by Sanofi and Medtronic.

We further disclose the following funding: C.P., N.B. and L.E received support by the Deutsche Stiftung für Herzforschung (German Heart Foundation, F/44/12 and F/11/17). G.F. received support by the Deutsche Gesellschaft für Kardiologie (German Cardiac Society). LE. and P.S.L. received support by the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich SFB 656 (project C11). F.K.W. received travel stipends by the Deutsche Gesellschaft für Kardiologie (German Cardiac Society).

Wegner FK, Bögeholz N, Leitz P, et al. Occurrence of primarily noninducible atrioventricular nodal reentry tachycardia after radiofrequency delivery in the slow pathway region during empirical slow pathway modulation. Clin Cardiol. 2017;40:1112–1115. 10.1002/clc.22797